A flash memory is used as a file memory for saving data in an electronic device such as a computer or digital camera.
The bit cost of the flash memory has been reduced year by year by continuously increasing the capacity and advancing micropatterning. The number of applications of the flash memory has increased due to the increased capacity and scaling of the device dimension. Recently, the bit cost of the flash memory has been reduced by a bit cost scalable configuration (a three dimensional stracked array structure) in addition to the scaling of the device dimension and multilevel cell.
In the bit cost reducing technique like this, the signal amount of a cell basically reduces, and the capacity of a bit line for reading out a signal from the cell increases, so the read speed of each cell decreases. Also, to reduce the bit cost, it is necessary to finely perform a write operation and verify operation. This decreases the write speed as well.
A conventional semiconductor memory device incorporates a page register that allows high-speed read and write from an external device. The bit size of this page register is called a page length. The unit of read or write performed for memory cells at once is called a page. The bit size of the page is also called a page length. Data having the page length is read out or written at once between the page register and memory cells. The page length is much larger than the number of input/output bits of a memory chip. Accordingly, the semiconductor memory device can perform data transfer at high speed with an external device by obscuring slow operations of an internal memory cell array.
To process large amounts of stored data, it is necessary to improve the high-speed data access performance. The development of a speed increasing technique of increasing the bandwidth five to ten times, e.g., from 200 to 400 MBytes/sec has been advanced.